Field of the Invention
The present invention relates to an imaging device.
Description of the Related Art
In recent years, CMOS image sensors that allow for low power consumption and fast readout are widely used as an imaging device for an imaging system such as a digital still camera, a digital video camera, or the like. As a readout method in the imaging device, global electronic shutter has been proposed in which the start time and the end time of charge accumulation are common to all the pixels.
Within each pixel of an imaging device disclosed in Japanese Patent Application Laid-Open No. 2009-272374, in addition to photoelectric conversion units that perform photoelectric conversion, charge holding units that hold charges generated by the photoelectric conversion unit for a predetermined period are provided in order to implement a function of global electronic shutter. When a light enters the charge holding unit, charges photoelectrically converted by the charge holding unit form a false signal, which may cause deterioration of the image quality. Thus, a light-shielding portion covering the charge holding units is provided in the imaging device of Japanese Patent Application Laid-Open No. 2009-272374.
In the art of Japanese Patent Application Laid-Open No. 2009-272374, a plurality of edges of openings of the light-shielding portion are arranged near ends of the charge holding units in a top view, which may result in insufficient shield of a light. Therefore, a light entering the charge holding unit may cause a false signal resulting in deterioration of the image quality.